Apparatus for heat-treating gun bores



July 23, 1940. H. E. soMEs 2,208,607

APPARATUS FOR HEAT-TREATING GUN BORES Original Filed Jan. 21, 1957 I 5 Sheets-Sheet 1 l I m 1 mu. s- 2 8 IIMEI P161 94 VINVENTOR.

4- HOWAYQDE. Som s. 8e r F c7' 1 BY M I /0 p /0. 7 9 Mo ATTORNEY.

July 23, 1940.

H. E. SOMES APPARATUS FOR HEAT-TREATING GUN BORES Original Filed Jan. 21, 1937 5 Sheets-Sheet 2 mvsmon. HowARDESoMEs ATTORNEY.

July 23, 1940. H. E. SOMES APPARATUS FOR HEAT-TREATING GUN BORES Original Filed Jan. 21, 1937 5 Sheets-Sheet 5 ooooooooooooooo EICLii INVENTOR. H OWARDE 5 OMES.

ATTORNEY.

July 23., 1940.

I H. EQSOM'ES APPARATUS FOR HEAT-TREATING GUN BOI RES Original Filed Jan. 21, .1937 5 Sheets-Shet 4 INVENT OR. HOWARDE-5OM$ ATTORNEY.

July 23, 1940. SOMES 7 2,208,607

APPARATUS FOR HEAT-TREATING GUN BORES Original Filed Jan. 21, 193'? 5 Sheets-Sheet 5 INVENTOR. HOWARD 5. 501425.

- ATTORNEY.

Patented July 23,

I 2,208,607 APPARATUS ron HEAT-TREATING GUN norms PATENT OFFICE Howard E. Somes, Grosse Pointe Park, Mich.

Application January 21, 1937, Serial No. 121,598

Renewed April I, 1939 21 Claims.

The title of this invention indicates the class.

to which it belongs. The figures of the drawings following show one embodiment of my invention.

As usual it is susceptible of many others. 6 Fig. 1 is a vertical side elevation of the ap- D ratus.

Fig. 2 is afront elevation at right angles to Fix. 1.

Fig. 3 is a transverse cross section of the ver- 10 tical framework of the apparatus. I

Fig. 4 is a plan view of the lower bracket arm.

Fig. 5 is a plan view of the end of the supporting arm.

Fig. 6 is a plan view at the top of the base block supporting the work. 4.

Fig. '7 is a side view in vertical axial section of the switching transformer and tool carriage, on an enlarged scale.

Fig. 8 is afragmentary enlarged view of the 20 upper end of the machine.

Fig. 9 is a fragmentary enlarged view of the lower end of the machine.

Fig. 10 is a transverse section of the quenching mechanism feed on line 5-5 of Fig. 1.

Fig. 11 is a detail of the quenching spray head.

Fig. 12 is a longitudinal sectional view of a gun treated in accordance with-the invention.

Fig. 13 is a circuit diagram of the control system.

The central object of theinvention is the achievement of a method and an apparatus whereby the bore of a gun can be heat treated by high frequency induction. So, far as .I am aware this has never been achieved prior to my invention.

axial portions-of the bore, and as thecurrents' are so shifted, quench the. heat which has been.

generated by the currents so circulated and 5 shifted. Preferably I uniformly progress. the

axially shifting currents which achieve the'heating, and uniformly progress the quench of those heated portions from which the current has been shifted. Preferably during the .process of shift- 5o ing I maintain a determinate axial spaced relation between the zone traversed by the currents and the zone subjected to the following, quench so that the zone of the bore which has been heated fully to quenching temperature will precede this space.

65- From another angle it may be said that I prefer barrel, and after According to the method of my invention there to maintain between the zone traversed by the progressing induced currkot-andthe zone being quenched a zone which has been heated to quenching temperature by the axial shifted current but momentarily free from substantial influence of either the shifting current or the quench. Preferably I begin the inducing of the treating current outside of the barrel and of an intensity and volume approximating that which shall be generated within the barrel and similarly end theinducing of current of similar intensity and volume at the opposite end of the-gun, also outside of the barrel. The current, the inducing of which has so begun and so ended, is progressively shifted in the one case into one end of the being progressed throughout the extent of the bore is similarly shifted out of the opposite end thereof.

The apparatus for carrying out this method comprises means to support the gun with free 'spacesubstantially equal to its length disposed axially beyond each end thereof and freely accessible from the end. In the'free space at one end is a mechanism for progressing into along, back along and again out of the bore of the gun a high frequency induction work coil of a dimension adapted to induce in the surface of the bore and in proper proximity thereto, the heating currents desired. Occupying the spaceat the opposite endof the gun is a mechanism for introducing to the bore progressing therealong, back therealong and then out again, a quenching head through which quenching fluid may be projected upon the heated bore to be quenched. Coordinated motor driving devices for these two devices, and an into-device spacing mechanism between the high frequency induction work coil andt-he quenching head insure their coordinated traverse of the bore of the gun :from one end to the other in proper spaced relation. -A chronometrically driven controller insures ,a coordinatedactivity of the various parts ofthese devices in their functional r'e- REISSUED APR 7 194 lations to eachother individually and collectively. Y

A means to introduce a dry inert gas under pressure to the bore being treated and progressing it under pressure between the high frequency in I duction coil and the bore and countered .to the flow of the quenching medium prevents vaporized and sprayed quenching medium and other moistures from engaging upon the heated surfaces of the bore and thereby attains its treatment without marringsits surfaces, either through oxidation, de-carbonizing or through electrical faults brought about by the excess presence of moisture. Referring then to thedrawings, i0 is the gun,

' centered upon a flanged centering ring 13 borne I l is the main frame of the apparatus both verticaL'and founded upon the floor l2 of the shop, or other platform upon which the equipment is to be used. The gun points vertically upward and at its end which is at the floor i2 is seated and through the swinging link pin l9 engaging its opposite side in a well known manner.

The standards H of the main frame of the machine are anchored to the concrete floor or other platform l2 in any suitable manner and projecting vertically upward. They support the upper end of the gun II! by means of a laterally projectv ing arm 20, which arm is vertically adjustable link pin coupler 3|.

up and down the reduced cross section2| of the standard I I and clamped in any adjusted position by means of the bolts 22 which connect together the halves which embrace the shaft 2|. The'end which engages the muzzle of them i0 is also made in two halves, as indicated at 23, the one of which is integral with the arm and the other swingable about the pivot 24 to engage and center the upper end of the gun through the v-shaped jaws 25 and thereafter be clamped firmly thereupon by the link pin 26-connecting together the opposite ends of the halves from the pivot 2|. Between the floor level I2 and this,

verse inter-column brace member 21 for the three columns l0. Such a brace is located also at the extreme upper end,.it will be seen, and as many of these inter-column braces may be utilized at different points as it may prove expedient to use. Each of these comprises a generally triangular main body, one apex of which, 28, is made in halves and fixedly clamped about the central column II and the two other apices of which are made in halves bridged by a common hinged bridging member 29 pivoted by a hinge 30 to the main body 21v and coupled to the main body at the end opposite the hinge 30 by means of the These members 2'! engage. shoulders-32 respectively upon the columns, They do not'engag'e the barrel of the gun. Instead, the main body is provided with an opening 33 concentric with the axis of the gun and large enough for the barrel to pass freely therethrough. If demoved therefrom without dis-assembly of the apparatus and to be placed in position laterally rather than raised or lowered vertically into position.

Onthe upper portion of the main frame col- Y umn II are mounted upper andlower 'swingable bracket arms 34 and'35, at opposite endsof a spacing sleeve 36, the upper bracket arm 36 being mounted upon the reduced upper portion of the by means of a clamping nut 38, while the lower a bracket arm is split where it surrounds the (51- umn and arranged to be clamped thereon by means of suitable clamp bolts 39. The swinging bracket arms 38 and 35 form a support for the tool carriage Alli which it supports on a rotatable feed screw shaft 4| journaled at opposite ends 5 in the upper and lower bracket arms 34 and 35 by means of suitable ball bearing journals 42 and 63 respectively, the screw shaft H being arranged 'to be rotated by means of a bevel gear -43 secured at its upper end by means of a suitable key 10 45 and driven by'a complementary bevel gear as carried at the end of the shaft of the motor 47 mounted upon the top of the upper bracket. arm 34.

The screw shaft 6| threaded portion 48 of the carriage through which 'it passes for elevating and lowering the carriage according to the direction of rotation of the screw shaft. The bracket 49 mounted on 20 the carriage carries the heating coil supporting rod 66 and a motor cylinder 50 which movably supports the casingil of a switching transformer.

'I'he transformer casing 5| is supported for 26 work cylinder about the rod 66. The transformer casing comprising upper and lower portions 30 54-45 is, provided in its lower portion with 9. cylindrical transformer primary element 56 comprisinga cylindrical laminated bore element 51 carrying nested within its inner cylindrical surface the primary transformer winding 58 whose terminals 59-450 extend outwardly through the transformer casing for conneetionwith a suitable source of alternating current, not shown. Mounted within the transformer casing 5| is the secondary transformer element 62comprised in 40 general of the secondary transformer winding 63 imbedded in the outer surface portion of a hollow laminated core element 64, the whole assembled between end plates 65 and carried upon the hollow vertical slide rod -86 in fixed relation 48 therewith so that when the piston 53 of the-work cylinder 50 is moved to its lowermost position in the cylinder, the secondary transformer element 62 will remain stationary while the transformer casing 5| will move downwardly relative thereto.

This relative movement will bring-the priinary transformer element 58 and with it the primary winding 58 down over thelaminated core extension 6 l, the latter providing a low reluctance cor element for theprimary winding. s

The hollow rod 66 is held flxedin relation to the cylinder 50 and bracket 49 at its upper end by means of the shouldered portion 81 and the nut 58, the transformer casing 5| having sliding bearing on the rod 66 through the tubular piston rod 52.

The hollow rod 66 has sliding bearing in the.

bushing 69 in the bracket 35 through which bushing it extends down into and through the barrel of the gun Hi to the breech end where it carries the inductive heating coil lil which in its t0 the terminals of theheating coil 70. v Cooling g is in driving engagement 15 with the tool carriage til through the lntemal water is circulated through the tubular conductors II for supply of cooling liquid to the transformer secondary coil and. the heating coil 10 by means of the upper extensions of the tubes 13 g which extend up through the hollow tube above the bracket 49 asindicated at 14 where they may be connected with any suitable source of supply of cooling fluid not shown.

The chamber H is formed with an internal diameter the same as that of the'bore of the gun andv is lined with a radially laminated wall 15 extending up to form a laminated lining or protecting sleeve I8 for the threaded portion of the gun breech. The function of this laminated lining is to provide a low impedance magnetic circuit for the heating coil 10 for a purpose to be hereinafter explained in connection witlrthc description of operation.

Like the secondary transformer element 62 the heating coil 10 is formed of a hollow conductor carried upon a cylindrical radially laminated core element 11, but withan outside diameter proportioned to pass freely' through the barrel of the gun out of contact therewith and in close proximity to the surface of the bore.

At the muzzle of the gun I I provide an upper terminal chamber I8 similar to the lower terminal chamber 15 and like the chamber 15 provided with a radially laminated lining or wall 19, so positioned and proportioned as to receive and surround the heating coil 10 when the latter is drawn up thereinto, to provide a low reluctance magnetic circuit for the coil. The chamber 18 is hermetically sealed to the muzzle of the gun i 0 by means of the gasket element 80 fitted between the lower opening of the chamber and the muzzle of the gun, and a stuffing box 8| at the top of the chamber for the hollow rod 56. Pressure control valve 82 connected with the upper end of the terminal chamber 18 provides for the introduction of a dry inert gas under pressure from a suitable source not shown, whereby the, chamber 18 and the gun barrel i0 may be maintained filled with an inert gas under pressure, the gas passing on down through the.clearance between the heating coil I0 and the bore of the gun into the lower terminal chamber 1| to an outlet conduit 83 which latter provides an outlet permitting complete displacement of air or other undesirable substance from the gun bore by the inert'gas.

A lower extension 84 of the bottom terminal chamber II extends down through the supporting floor I 2 into communication with a quenching fluid exhaust chamber 85. Through this chamber a sliding quench-tube 86 passes up into the lower extension 84 of the lower terminal where the tube carries a quenching head 81 spaced from and. substantially sealed off-from the heating coil 10 by means of a piston head 88 and center projection 89 fitting intothe open end of the hol-, low core of the heating coil I0. The tubular rod 86 enters the exhaust chamber 85 through suitable stuinng box 90-and is mounted for vertical movement to progress the quenching head 81 up through the lower terminal chamber H into and through the bore of the gun to the upper or muzzle end ofthe gun, and to thereafter retract the quenching head back to its lowermost position shown in Fig. 9 of the drawings.

.Movement of the quenching head is properly coordinated with the movement of the heating coil 10 to follow'the upward movement of the heating coil through the gun barrel. in constant spaced relation to the coil as determined by and vertically sliding rack element 93 carrying; bracket 94 to which the lower end of the tube 86 is fixed. The driving motor is adapted to exert suflicient lift on the tube 86 to cause it to follow the heating head upwardly through the gun barrel and without undue upward pressure on the heating coil. A stationary brace and guide element for the rack 93 extends vertically between the floor support I2 and a lower stationary bracket sup-port 96. The quenching fluid is supplied to the tubular rod 86 by means of a flexible hose connection 91 at the lower end of the tube. Exhaust quenching fluid is drawn off from the exhaust chamber 85 through the outlet conduit 98 and pressure valve 99 and a trap or gas and liquid separator I00 for separating such of the inert gas as may pass downwardly into the exhaust chamber 85.

Operation of the pneumatic motor cylinder 50 is controlled through an electro-magnetically operated control valve IN and piston valve I02 operable in known manner upon energization to exhaust the top of the cylinder 50 and admit air to the bottom thereof to raise the piston 52 to the top of the cylinder and upon deenergization to exhaust the lower end of the cylinder and admit air to the upper end to effect downward movement of the piston thus operating upon energization to raise the transformer shell 5! into the position shown and upon deenergization to effect lowering of the transformer shell to move the primary winding 63 out of cooperative relation with the secondary winding 64 and into cooperative relation with the low reluctance magnetic circuit element 6 I.

To insure operation of the various parts in proper sequence for carrying out a complete operation on a gun barrel, I provide the control svstem and chronologically. driven controller therefor diagrammatically shown in Fig. 13 of the drawings. In this diagram, the controller which is preferably in the form of the usual commutator drum element I03 of insulating material is here shown opened out into a plane surface development of its cylindrical surface, the top and bottom edges of which represent the same generating line of the cylindrical surface. Thedrum of insulating material has formed thereon or in-set therein various commutator sectors such as S, L, etc. for effecting electrical contact with stationary contact brush elements S, L, etc. respectively during rotation of the drum and in proper sequence. To effect proper timing of the sequence of circuit closure by the controllenthe drum I03 is arranged to be rotated at a predetermined rate by means of a suitable driving motor I04, preferably a synchronous motor and through suitable reduction gears I05. Current for the control system may be derived fromany suitable source of 1 current supply here indicated as an ordinary'commercial line 106, which for the sake of simplicity in circuit connections is shown as having the lower side earthed or grounded as indicated by a ground symbol E and the upper side free or ungrounded, such connections as lead from the apparatus to the grounded side of the line being indicated by a similar ground connection symbol. As indicated in the circuit diagram, the control commutator drum I03 is provided with a starting signal control segment S permanently connected to the free side of the line 7 through conductor I01 while all of the other segments L, HD, G, etc. are connected to the free side of the line through normally open contact 108 of a locking relay I09 by way of conductors I I and III. Thus, the segment S will always effect a connection from the free side of the line to its associated brush 8' while all of the other segments L, HD, G, etc. are operative to effect connection of the free side of the line to their associated brushes L, HD', G, etc. only during closure of the contact I08 of locking relay I09.

For control of the traversing motors 41 and EH for raising and lowering the heating coil 10 and quenching nozzle 81, respectively, the motors 41 and 9| are provided with pole-changer switches H2, H3 respectively suitably arranged for effecting the proper change of polarity for reversing their respective motors in any suitable manner according to the type of motor. As the two motor circuit diagrams are alike, it will be necessary to describe but one of them, for example, that of the heating coil traversing motor 41 which it will be noted comprises the pole-changer switch II2 heretofore mentioned arranged to be normally held in an open circuit position as by the centering retractile springs 4 connected to the pivoted arms N5 of the switch below the pivotal points, the pivoted arms of the switch being arranged to be moved to one side or the other by solenoids or magnets H6, H1, respectively, to energize the motor for rotationin one or the other direction for bringing about a downward or upward movement of the heating coil 10. Similarly, the pole-changer switch H3 is moved to the right or left by magnets H8 and H9, respectively, for movement of the quenching head 81 downwardly and upwardly. The control .of pressure fluid to the motor cylinder 50 is eifected by an electro-magnetic valve IOI, control of the inert gas supply to the pressure control valve 82 is efiected through an electro-magnetic valve I 20 and control of the quenching fluid from a suitable source of supply to the flexible hose connection 41 leading to the quench-head 81 is efiected by an electro-magnetic valve I2I. One terminal of each of the operating magnets H6, etc. and the electro-magnetic valves IOI, etc., is connected to the grounded side of the line I06 as diagrammatically shown while the ungrounded terminals of each of such operating magnets and electro-magnetic valves are arranged to be connected to the free side of the line I08 at predetermined intervals through their respective control brushes and commutator segments on the controller I03. The controller also governs the connection of the primary winding 56 of the switching transformer to a source I22 of high frequency current through an electro-magnetically operated line switch I23.whose operating magnet like the various other operating magnets has one terminal normally grounded and the other terminal arranged to be connected with the free side of the line I06 through a brush and commutator segment of the controller. A starting segment I24 and starting push button I25 complete the control equipment.

In operation, assuming that a gun to be operated upon is in position in the machine as shown in the several drawings, the upper terminal chamber 18 in place on the muzzle of the gun ID in sealed relation thereto, the heating coil element 10 in the raised position and wholly within the upper terminal chamber, the quench-head 81 in the lowermost position as shown in the several views, and the various circuits and apparatus elements of the control system in the position indicated in thediagram Fig. 12 with the controller drum I03 rotating to move the various commutators S, L, etc., in the direction indicated by arrow adjacent to the drum, continued rotation of the drum from the position shown first brings the commutator segment S, normally connected to the free side of the line through conductor I01, into contact with its associated brush thus connecting the free side of the line to the ungrounded terminal of the starting signal lamp I24 which lights the lamp indicating to the operator that the controller is ready to start its cycle of operations. The operator may then start the cycle of operations by pressing the starting button I25 which completes the energizing circuit of the locking relay I09 over a path which may be traced from the grounded side of line I06 through locking relay I09, push button I25, controller brush S, segment S, conductor I01 to the free side of line I06. Locking relay I09 upon energization attracts its armatures connecting the free side of line I06 through conductor III and normally open contact I08 (now closed) to conductor IIO through which the connection from the free side of line is extended to all of the controller segments L, HD, etc., excepting the starting segment S as indicated by the dotted line extension of conductor IIO through the controller drum. The locking controller segment L having made contact with its associated brush L' ator immediately after connection of the starting segment S with its associated brush, the energization of the locking relay I09 completes its locking circuit through this locking segment over a path which may be traced from the grounded side of line I06 through relay I09, locking contact I 26, circuit controller segment L, conductor "0 to free side of line as previously traced through contact I08 of the locking relay. The locking relay I09 thus remains energized maintaining all of the controller segments connected to the free side of line during the passage of the long locking segment L under its associated brush L.

The controller segment HD now engaging its associated brush HD' completes a circuit from the free side of line through brush HD, to the operating magnet I I6 which, becoming energized, moves the pivoted blades of the pole-changer switch II2 to the left completing the circuit of motor 41 to the line I06 through branch conductors I21 to cause operation of the'motor 41 in a direction to move the heating coil 10 downwardly from the upper terminal chamber 18 through the bore of the gun and into the lower terminal chamber H as indicated in Fig. 9 of the drawings. Immediately after the heating coil 10 starts its downward movement the controller segment G starts engagement with its associated brush G through which it efiects connection of the free side of line I06 to electro-magnetic valve I20 to energize the same and connect the pressure control valve 82 to a suitable source of supply of dry inert gas. The dry inert gas thus enters the upper terminal chamber 18 as the heating coil leaves the chamber, following the coil down and continuing to fill and maintain the bore of the gun filled under suitable pressure during the downward movement of the heating coil and continuing after the heating coil reaches its lowermost position, the gas escaping through the clearance between the heating coil and the sides of the lower terminal chamber and out through the vent conduit 83. The length of the by providihg the motor 41 in the form of a constant torque motor .or by'providing a suitable slip clutch connecting between the motor and the driving screw ll or by the provision of suitable resilient or elastic lost-motion means. After the segment I-ID has passed beyond its complementary brush HD' and the heating head 'l'll'has come to rest at the lower position shown in Fig. 9,

the line switch segment LS engages its associated brush LS to connect the free side of line I06 yvith the operating magnet of the electromagnetic line switch I23 which thereupon connects the primary winding 56 of the switching transformer with the source of high frequency current I22. However, the heating coil I is not energized at this point because of the fact that, as shown in the diagram in Fig. 13, the primary winding 56 is uncoupled from the sec- 'ondary winding 63. Soon after this point in the cycle the commutator segments QV and ST for controlling the supply of quenching fluid and for actuating the switching transformers, respectively, Pass into engagement with their respective associated brushes QV' and ST. The commutato'r segment QV effects connection of the free side of line I06 through commutator segment QV' to the electro-magnetic control valve |2I ing coil I0 and the quenching head 81 upwardly,

which, becoming energized, connects the quenchhead B'I through flexible hose. connection 91 to,

a suitable source of supply of quenching fluid under pressure. The commutator segment ST connects the free side of line I06 through its complementary brush ST to the electro-magnetic va'lve IOI which energizing admits air to the lower end of motor cylinder 50 raising the transformer shell and with it the primary transformer winding 56 of the switching transformer into a transformer coupling relation with the secondary winding 62. The heating coil 10 is now energized from the secondary winding 62 over the hollow conductors I3. With the heating coil thus energized and the quenching head operating to spray quenching fluid outwardly in the space surrounding the quenching head below the heating coil, the commutator segments HU and QU'move into contact with their respective brush elements Hi1 and CW to connect the free side of line I06 with the operating magnets Ill and N0 of the pole-changer switches H2 and M3 to connect the motor 41 and SI through the branch circuits I21 and I28 respectively to the line circuit I06 in a manner to cause the motors to rotate in a direction to move both the heatthrough the barrel of the gun, the quenching head 01 following the heating coil upwardly through the barrel until the heating coil enters and comes to rest in the upper terminal chamber ll, at which time the segments HU and QU pass from under their respective brushes to deenergize the control magnets Ill and H9 which in turn permit restoration of the v pole-changer .switches to the intermediate or open circuitposition thus effecting deenergization of their remotors 41 and 9| is so timed that the heatingcoil will move upwardly through the bore of the gun, at the constant rate required to effect the proper heating followed by the quenching head 81, the quenching head following always in abutment against the lower end of the heating coil 10 through the'spacing piston diaphragm 88 to insure constant spaced relation between the zone heated and the point of application of quenching fluid. The parts may be coordinated in any suitable manner to insure this following of the coil by the quench-head as by accurate timing of the motors or, preferably, by having the motor SI of a constant torque type, designed to overcome the weight of the spray head and its movable parts with suflicient margin of power to urge the quenching head upwardly always in contact with the bottom of the heating coil I0.

After the heating coil enters the uppermost terminal chamber I8, the commutator segments HU and QU moving out of contact with their respective brushes HU and QU' open the circuit of the magnets Ill and 9 to deenergize the motors l1 and 9|. Movement of the heating coil all the way up into the upper terminal chamber followed all the way by the quenching head both stopping in their extreme upper positions without undue strain on the machinery may be assured in.

any known or other suitable manner as suggested in connection with the stopping of the heating coil in its lowermost position within the lower terminal chamber 1|. Upon entrance of the heating coil into the upper terminal chamber, the segment G of the controller passes out from under its associated brush G breaking connection between thefree side of line I06 and the brush G. This deenergizes electro-magnetic valve I'20 cutting oif the supply of gas to the regulating valve 82. Substantially at the same time, the switching transformer control segment ST passes out of contact with its associated brush ST disconnecting the free side of line I06 from this brush thus deenergizing electro-magnetic valve IOI which operates to exhaust pressure fluid from the bottom of the motor cylinder 50 and admit pressure fluid to the top thereof to move the casing of the switching transformer downwardly and with it the primary winding 50 restoring the switching transformer to its uncoupledposition. Movement of the switching transformer to uncoupled position brings the primary winding 56 into inductive relation with the low reluctance magnetic circuit furnished by the laminated core'extension 6| to prevent unfavorable change in the reactance .of the circuit of the switching transformer.

After uncoupling of the switching transformer 56, the control segment LS moves out of contact with its associated brush LS disconnecting the free side of line I06 from the latter and thereby .deenergizing the electro-magnetic line switch I23 and disconnecting the primary coil 56 from the source I22 of high frequency current. The commutator segment QV now passing out of contact with brush QV' opens the circuit of the electromagnetic control valve I2 I which deenergizing cuts off the supply of quenching fluid from the quenching head 81. Control segment QD now moves into contact with its'associated brush element QD' connecting the free side of line I06 to said brush and thereby completing the energizing circuit of operating magnet H8 of pole-changer switch I I3 which magnet upon energization moves the switch I II to the left to connect thelmotor 9| through'extension conductors I28 to the line I06 for reverse movement to effect downward move- I which permits the pole-changer switch 3' to move into open circuit position, deenergizing motor 9|. The length of the segment QD is so proportioned in relation to the speed of the motor 9| and the speed of the controller I03 as to effect this deenergization of the motor when the quenching head 8! reaches its lowermost position. Any

known or other suitable means, not shown, may

be provided to enable the quenching head 81 to come tq rest incthe position shown in Fig. 9 of the drawings without undue shock to the mechanism and without imposing undue load on the motor 96, such for example as the use of a slipping clutch connection or resilient lost-motion connectlon between the quench-head tube 86 and the driving motor or by suitable selection of the electrical characteristics of the motor. After the segment QD passes from under its brush QD', the locking circuit segment L passes from under its associated brush L' opening the locking circuit of relay I09 previously maintained through this segment and the locking contact I26. The initial energizing circuit of relay I09 being open at the push button I25, the relay becomes deenergized opening the connection between conductor H0 and the free side of line I06 at contact I03 thus removing the line connections from all of the commutator segments except the starting-signal segment S. I

The controller thus restored to normal with the various apparatus and circuit elements in the position as shown in Fig. 12 leaves the apparatus in a position with the heating coil 10 in the upper P essure chamber 18 clear of. the muzzle of the gun, and the quenching head 81 in tlie lowermost position as shown in Fig. 9 of the drawings outside and clear of the breach of the gun. The gun thus heat-treated is now free to be removed from the machine after release -from the various clamping and holding'.elements such as the arms 20 and 21 and the centering clamp I1.

A gun so treated is shown in Fig. 12 of the drawings where the heat-treated portion near and including the inner surface of the bore is indicatedat I29.

During upward movement of the heating coil I0 closely followed by the quenching head 81, quenching fluid is kept out of contact with the coil or the clearance space between the coil and the bore of the gun by means of the separating piston member 88, leakage of quenching fluid beyond the piston through the slight clearance between the piston and the walls of the gun bore being prevented by the presence of the inert gas under pressure in the spacesabove the quenching head and by the downward passage of such gas through the clearance between the separating piston 88 and the walls of the gun bore. Any gas passing out through the quenching fluid outlet conduit 48, (where a liquid quenching fluid is used) may be separated off from the liquid by liquid trap llll (Fig. 1). i a

Inasmuch as the heating coil Hi is initially energized for its upward movement through the barrel of the gun before entering the breech of the gun and is maintained energized after leaving the mumle to insure'an ev en treatment of the gun barrel throughout its length, it is desirable to maintain the electrical characteristics of the heating coil-substantially constant during such aaoaco'a movement and during its complete time or energization. This is to insure that the energy output of the coil will remain substantially constant throughout its passage through the gun barrel coil Ill substantially constant throughout its travel from the lower terminal chamber to the upper terminal chamber, or otherwise aflect such reactance to prevent undesirable change in power factor due to removal of the coil from the surrounding low reluctance material of the gun.

While I have herein shown and described a pre- I ferred embodiment of my invention for the sake of disclosure, it is to be understood that the invention is not limited to the specific embodiment shown and described, but contemplates all such variants and modifications thereof as fall fairly within the scope of the appended claims.

What I claim is:

1. An a paratus of the type described comprising means for holding an object having a cylindrical bore an induction heating element arranged to be moved into and out of the bore of the object held by said holding means, a quenching nozzle arranged to follow said heating element into the bore near the trailing end of the heating element, and means for maintaining an inert gas in the bore on the side of theheatin element rem.--te from the quenching nozzle and in the clearance between the heating element and the bore. V l

2. An apparatus of the type described comprising means for holding an object having a cylindricalbore, an induction heating element arranged to be oved into and out of the bore of the object he (1 by said holding means, a quenching nozzle arranged to follow said heating element into thebore near the trailing end of the heating element, and means for maintaining a magnetic induction heating element less in length than the length of the inner surface to be treated.

and provided with an internal core only, and arranged to have its magnetic circuit completed substantially wholly bythe material of said object, means for moving the heating element from a point outside the object intoand through the hollow of the object to a point outside the object, and'low reluctance means arranged at each-end of the object to form a substantially continuous extension'o'f the object and to contain the entire portion of the heating element not contained in the work piece object during the entire entrance and withdrawal i movement of the heating element.

4. Apparatus for heat-treating elongated hollow cylindrical objects of magnetic material at and near the inner surface comprising an electromagnetic induction heating element less in length than the length of the inner surface to be treated and provided with an internal core only and arranged to have its magnetic circuit completed substantially wholly by thematerial of the said 

